src/main/java/Inventory/Inventory.java

@@ -6,20 +6,19 @@ import Item.ItemStack;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
-import java.util.stream.IntStream;
 
 public class Inventory {
     private final List<ItemStack> items;
-    private final int weightLimit;
+    private final int maxWeight;
 
     public Inventory() {
         items = new ArrayList<>();
-        weightLimit = 100;
+        maxWeight = 100;
     }
 
     public Inventory(int weightLimit) {
         items = new ArrayList<>();
-        this.weightLimit = weightLimit;
+        this.maxWeight = weightLimit;
     }
 
     public List<ItemStack> getItems() {
@@ -27,38 +26,28 @@ public class Inventory {
     }
 
     public void addItem(ItemStack stack) {
-        boolean isSingleItem = stack.getQuantity() == 1;
-        if (isSingleItem) {
-            if(stack.getItem().getWeight() > weightLimit) return;
-            items.add(stack);
+        if (stack.getWeight() + getCurrentWeight() > maxWeight) {
+            if(stack.isSingleItem()) return;
+            trySubstack(stack);
+            return;
         }
-        if (stack.getWeight() + getCurrentWeight() > weightLimit) addSubStack(stack);
         items.add(stack);
     }
 
-    private void addSubStack(ItemStack stack) {
-        int maxQuantity = calculateMaxQuantity(stack);
-        items.add(new ItemStack(stack.getItem(), maxQuantity));
+    private void trySubstack(ItemStack stack) {
+        int stackSize = getMaxStackSize(stack);
+        if (stackSize == 0) return;
+        items.add(new ItemStack(stack.getItem(), stackSize));
     }
 
-    private int calculateMaxQuantity(ItemStack stack) {
-        int maxQuantity = 1;
+    private int getMaxStackSize(ItemStack stack) {
         int weight = stack.getItem().getWeight();
 
-
-        for (int i = maxQuantity; i <= stack.getQuantity(); i++) {
-            int currentWeightWithStack = (weight * maxQuantity) + getCurrentWeight();
-            boolean weightOutsideLimits = currentWeightWithStack >= weightLimit;
-            if (weightOutsideLimits) {
-                break;
-            } else {
-                maxQuantity++;
-            }
-        }
-        return maxQuantity;
+        int maxSize  = (maxWeight - getCurrentWeight()) / weight;
+        return Math.min(maxSize, stack.getQuantity());
     }
 
-    private int getCurrentWeight() {
+     public int getCurrentWeight() {
         int  currentWeight = 0;
         for (ItemStack item : items) {
             currentWeight += item.getItem().getWeight();
@@ -78,4 +67,8 @@ public class Inventory {
         }
         return false;
     }
+
+    public int getMaxWeight() {
+        return maxWeight;
+    }
 }

src/main/java/Item/ItemStack.java

@@ -1,5 +1,7 @@
 package Item;
 
+import Inventory.Inventory;
+
 public record ItemStack(Item item, int quantity) {
     public ItemStack {
         if (quantity <= 0) {
@@ -14,6 +16,10 @@ public record ItemStack(Item item, int quantity) {
         return quantity;
     }
 
+    public boolean isSingleItem() {
+        return quantity == 1;
+    }
+
     public int getWeight() {
         return item.getWeight() * quantity;
     }